In a vehicle including an internal combustion engine, for example, when a fuel tank is refueled, since a volume occupied by a liquid fuel in an internal space of the fuel tank increases, a volume occupied by a gas phase region in the internal space decreases relatively, and a pressure in the gas phase region (hereinafter, referred to as a “tank internal pressure”) becomes higher than the atmospheric pressure. As a result, the evaporated fuel in the gas phase region accumulated in the fuel tank is going to get out to the atmosphere. If the evaporated fuel is released into the atmosphere, the atmosphere will be polluted.
Therefore, in order to prevent the atmospheric pollution caused by the release of the evaporated fuel into the atmosphere, a conventional evaporated fuel treatment device is provided with a canister having an adsorbent for adsorbing temporarily the evaporated fuel on a communication passage between the fuel tank and the atmosphere, so that the tank internal pressure can be suppressed low by adsorbing the evaporated fuel to the adsorbent of the canister.
Patent Document 1, for example, discloses an evaporated fuel treatment device including a fuel tank with a sealed structure by providing a closing valve (hereinafter, referred to as a sealing valve) for controlling a communication state between the fuel tank and the canister on the communication passage of the evaporated fuel between the fuel tank and the canister. In the evaporated fuel treatment technology according to Patent Document 1, during stop of the internal combustion engine, the sealing valve is closed and the canister is open to the atmosphere. When the internal combustion engine is stopped and there is a pressure difference exceeding an open valve determination value between the tank internal pressure and the atmospheric pressure, the sealing valve is opened and a variation of the tank internal pressure which is generated before and after opening the sealing valve is detected. If the detected variation of the tank internal pressure is less than a predetermined value, the sealing valve is determined to be in a closing failure.
The evaporated fuel treatment technology according to Patent Document 1 makes it possible to efficiently detect the closing failure of the sealing valve without causing a negative pressurization of the tank internal pressure in the normal control.